If you've not got a camera for your PSP then it's probably best if you stop reading at this point because it's a pretty integral part of this game. Using the camera you'll have to hunt down and catch your very own Invizimals, at which point you can train them up before throwing them in the ring to face off against their own kind. It's possible that you might get bored with your creatures, but don't worry you'll be able to trade them with your friends. HMV are selling copies of the game for £6, which'll save you almost £2 on the next best offers.